Component Video Switching
Dear Gary: Our home theatre setup includes the Panasonic TH-42PWD3 plasma display, the Marantz SR-14EX A/V Receiver and the Sony DVP-S9000ES progressive DVD player. Needless to say, both video and audio are superb. The system works flawlessly. Our next step is to upgrde to an HDTV receiver utilizing our DirecTV satellite setup we now have. But I’m not sure as to how to best complete this addition. In particular, from reading your articles about video switching, I don’t want to lose any signal by sending the relay through the SR-14EX. Progressive scan YPbPr signals should have a flat frequency to at least 12MHz. And HDTV requires an even higher frequency response. So should I go to a video switcher so I can retain the superb signal response I am now getting or go to an Extron switcher or similar high-end switcher? Additionally, most HDTV receivers utilize three component (YPbPr) outputs whereas the Panasonic has five HDTV inputs (YPbPr, H and V). I assume the H and V inputs are for sync purposes and if I sync on green, I can use the three YPbPr inputs for 1080i HDTV signals.
Bob Birchenough
Video Technical Editor Greg Rogers Comments
I don’t have any specific information on the bandwidth of the Marantz switching circuits. I would suggest that you visually compare the performance by passing the signal from your HDTV receiver through the Marantz vs. directly to the plasma display. If you want to be more certain of its performance, you could measure the frequency response of the Marantz switching circuits with an oscilloscope and a signal generator. The maximum possible HDTV signal frequency is 37.1 MHz, although SMPTE standards only require flat response (within 0.05 dB) to 30 MHz. A frequency response of -0.5 dB at 37 MHz should be transparent on even the best displays. You can use a sinewave generator or the multiburst pattern from an AccuPel HDTV Calibration generator (www.accupel.com) to make this measurement. If you decide to use an external switcher be sure that it is specified for HDTV signals. Many consumer video switchers are only designed for NTSC & PAL signal bandwidths. Signal bandwidths are usually specified at the -3.0 dB limit, so I would recommend a bandwidth of 100 MHz or higher for HDTV. Extron (www.extron.com) offers a number of high quality professional switchers. The H and V sync inputs are used only with RGB signals. YPbPr signals will always include embedded sync on the Y signal. Some HDTV receivers provide YPbPr signals, some provide RGB/HV, and some offer both. Your plasma panel will accept both. See my article on HDTV Signal Formats in Issues 43 and 44 for more information on the many variations of HDTV signals.
You can E-mail Widescreen Review @ mailto:editorgary@widescreenreview.com